One off my head is:
Element.equalTo(anotherElement) - compares to see if value in
current element is equal to value in second element. This I had to
implement on my own for password confirmation.

--- In validation@yahoogroups.com, "somematt" <matthew.a.frank@...>
wrote:
>
> i'm soliciting feedback on helper functions to make setting up page
> validation much easier. i have already considered
>
> * Validation.require: makes one or more fields required
> * Validation.requireAtLeastOne: requires at least one of the
given
> elements be entered (boolean OR validation)
> * Validation.requireAll: requires all fields as one unit,
though
> this unit itself is not required (boolean AND validation, but
better
> than what's already provided)
> * Validation.requireGroup: simplified version of
requireAtLeastOne
> specific to checkbox and radio button groups with the same field
name
> * Validation.currency
> * Validation.dateTime
> * yadda yadda, fulfilling all the basic validations.
>
> the important stuff to nail down is for the more complicated
> validations. let me know what you like and don't like.
>
> another tweak i've been considering is using something more like
jMock
> syntax, but i'm wondering if that would be any easier to use than
> well-named methods.
>
> if you want to add comments to the issue in the project tracking
area,
> feel free
>
> http://code.google.com/p/javascript-form-validation/issues/detail?
id=8&can=2&q=
>